1 /*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 *
11 * From: @(#)s_floor.c 5.1 93/09/24
12 */
13
14 #include <sys/cdefs.h>
15 __RCSID("$NetBSD: s_truncl.c,v 1.4 2013/11/13 12:58:11 joerg Exp $");
16 #if 0
17 __FBSDID("$FreeBSD: head/lib/msun/src/s_truncl.c 176280 2008-02-14 15:10:34Z bde $");
18 #endif
19
20 /*
21 * truncl(x)
22 * Return x rounded toward 0 to integral value
23 * Method:
24 * Bit twiddling.
25 * Exception:
26 * Inexact flag raised if x not equal to truncl(x).
27 */
28 #include "namespace.h"
29
30 #include <float.h>
31 #include <math.h>
32 #include <stdint.h>
33 #include <machine/ieee.h>
34
35 #ifdef __HAVE_LONG_DOUBLE
36
37 #ifdef __weak_alias
38 __weak_alias(truncl, _truncl)
39 #endif
40
41 #ifdef LDBL_IMPLICIT_NBIT
42 #define MANH_SIZE (EXT_FRACHBITS + 1)
43 #else
44 #define MANH_SIZE EXT_FRACHBITS
45 #endif
46
47 static const long double huge = 1.0e300;
48 static const float zero[] = { 0.0, -0.0 };
49
50 long double
truncl(long double x)51 truncl(long double x)
52 {
53 union ieee_ext_u ux = { .extu_ld = x, };
54 int e = ux.extu_exp - LDBL_MAX_EXP + 1;
55
56 if (e < MANH_SIZE - 1) {
57 if (e < 0) { /* raise inexact if x != 0 */
58 if (huge + x > 0.0)
59 ux.extu_ld = zero[ux.extu_sign];
60 } else {
61 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
62 if (((ux.extu_frach & m) | ux.extu_fracl) == 0)
63 return (x); /* x is integral */
64 if (huge + x > 0.0) { /* raise inexact flag */
65 ux.extu_frach &= ~m;
66 ux.extu_fracl = 0;
67 }
68 }
69 } else if (e < LDBL_MANT_DIG - 1) {
70 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
71 if ((ux.extu_fracl & m) == 0)
72 return (x); /* x is integral */
73 if (huge + x > 0.0) /* raise inexact flag */
74 ux.extu_fracl &= ~m;
75 }
76 return (ux.extu_ld);
77 }
78
79 #endif /* __HAVE_LONG_DOUBLE */
80